Optical modulator elements of spatial optical modulators may be applied in a wide range of optical fields (e.g., an imaging apparatus such as a camera, an image projecting apparatus such as a projector, an optically measuring technology using a computer hologram, and forming a wavefront of laser beam).
For example, an optical modulator element which has a transparent support member and a liquid whose refractive index is matched to the transparent support member is known. The liquid penetrates into the transparent support member. The optical modulator element controls a refractive index by controlling wettability between the transparent support member and the liquid electrically using an electro-wetting effect. This technology is shown in G. Beni, S. Hackwood, “AppL. Phys. Lett. Vol. 38. Issue 4 (1981, pp. 207-209)” and Japanese Patent Application Publication Nos. 2010-282103, 2005-275162, 2013-073976, and 2013-037210, for example.
However, such an optical modulator element using an electro-wetting effect has difficulty in controlling an interface position of the liquid at multiple values though this optical modulator element which can obtain a higher aperture ratio in comparison to a transmission type optical modulator element using a liquid crystal element.